/*

 * Licensed to the Apache Software Foundation (ASF) under one

 * or more contributor license agreements.  See the NOTICE file

 * distributed with this work for additional information

 * regarding copyright ownership.  The ASF licenses this file

 * to you under the Apache License, Version 2.0 (the

 * "License"); you may not use this file except in compliance

 * with the License.  You may obtain a copy of the License at

 *

 *     http://www.apache.org/licenses/LICENSE-2.0

 *

 * Unless required by applicable law or agreed to in writing, software

 * distributed under the License is distributed on an "AS IS" BASIS,

 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.

 * See the License for the specific language governing permissions and

 * limitations under the License.

 */

package com.bff.gaia.unified.sdk.schemas;



import javax.annotation.Nullable;

import java.util.concurrent.ConcurrentHashMap;



/**

 * A wrapper around a {@link Factory} that assumes the schema parameter never changes.

 *

 * <p>{@link Factory} objects take the schema as a parameter, as often the returned type varies by

 * schema (e.g. sometimes the returned-type is a list that must be in schema-field order). However

 * in many cases it's known by the caller that the schema parameter is always the same across all

 * calls to create. In these cases we want to save the cost of Schema comparison (which can be

 * significant for larger schemas) on each lookup. This wrapper caches the value returned by the

 * inner factory, so the schema comparison only need happen on the first lookup.

 */

class CachingFactory<CreatedT> implements Factory<CreatedT> {

  @Nullable

  private transient ConcurrentHashMap<Class, CreatedT> cache = null;



  private final Factory<CreatedT> innerFactory;



  public CachingFactory(Factory<CreatedT> innerFactory) {

    this.innerFactory = innerFactory;

  }



  @Override

  public CreatedT create(Class<?> clazz, Schema schema) {

    if (cache == null) {

      cache = new ConcurrentHashMap<>();

    }

    CreatedT cached = cache.get(clazz);

    if (cached != null) {

      return cached;

    }

    cached = innerFactory.create(clazz, schema);

    cache.put(clazz, cached);

    return cached;

  }

}